An image forming apparatus using digital technology, for example, an electronic copier has a fixing apparatus which fixes a developer image fused by heating to a paper sheet by applying pressure.
A fixing apparatus has a heating roller for fusing developer, for example, toner, and a pressurizing roller for applying a predetermined pressure to the heating roller. A predetermined contacting width (nip width) is formed in a contacting area (nip) between the heating roller and pressurizing roller. When a paper sheet is passed through the nip, a developer image is fused by the heat from the heating roller and fixed to the paper sheet by the pressure from the pressurizing roller. Recently, an induction heater is used in which a thin film of conductive metal layer is formed on the outside of a heating roller and the conductive metal layer heated by induction heating.
In a fixing apparatus for forming a color image, for example, it is known to ensure a sufficient nip width by placing an elastic layer between a shaft and a conductive metal layer used for induction heating, in order to ensure more contact width than that in a monochrome image forming apparatus.
However, when the driving force from a shaft is transmitted to a conductive metal layer through an elastic layer, the elastic layer is twisted and the rotations of the shaft and conductive metal layer are not synchronized.